The present invention relates to a resin solution composition which comprises an acid-modified butene-1/xcex1-olefin copolymer and which is suitable for paint or adhesive applications.
Crystalline polybutene-1, which has excellent tensile characteristics, etc., is traditionally used as a material for pipes and films. However, being sparingly soluble in organic solvents, crystalline polybutene-1 is not readily usable for paint or adhesive applications except by means of powder coating.
In the meantime, with regard to a coating-forming agent usable as a component of solution-type paints, adhesives or the like, a modified polybutene-1 has been developed to take advantage of the characteristics of crystalline polybutene-1 and to ensure remarkable coating properties. To give an example, Japanese Patent publication No. Hei 4-27245 proposes a modified polybutene-1 obtained by graft-modifying polybutene-1 with an unsaturated carboxylic acid or an anhydride thereof.
Nevertheless, a solution composition of this modified polybutene-1 lacks storage stability. When stored at 25xc2x0 C., the solution composition gelates in as short as 10 days, only to degrade the solution fluidity. For this reason, such a composition is not suitable for use as paints, adhesives or the like, where a coating should be formed in a uniform thickness.
Further, in paint or adhesive applications, this modified polybutene-1, which has a high melting temperature, cannot ensure satisfactory coating properties (e.g. adhesion property, water resistance, gasohol resistance) after low-temperature baking or heat sealing is practiced at 100xc2x0 C. or lower.
Hence, taking advantage of superior characteristics of a modified polybutene-1, the present invention intends to provide a resin solution composition suitable for paint or adhesive applications, which composition can show good storage stability and form a coating with remarkable properties as a paint or adhesive, with the resin having a low melting temperature.
In order to achieve the above object, the inventors of the present invention have made intensive researches and completed the present invention.
To be specific, the present invention relates to a resin solution composition for paints or adhesives which comprises an acid-modified butene-1/xcex1-olefin copolymer obtained by modifying a butene-1/xcex1-olefin copolymer with an unsaturated carboxylic acid or an acid anhydride thereof. The butene-1/xcex1-olefin copolymer comprises 65 to 85 mol % butene-1 component and 15 to 35 mol % xcex1-olefin component as polymerizable components, the xcex1-olefin component having 2 to 8 carbon atoms and being other than butene-1 component. The acid-modified butene-1/xcex1-olefin copolymer comprises the unsaturated carboxylic acid or the acid anhydride thereof in a proportion of 0.5 to 5% by weight, and wherein the acid-modified butene-1/xcex1-olefin copolymer is dissolved in an organic solvent, in a solid content of 10 to 30% by weight.
In an embodiment of the present invention, the acid-modified butene-1/xcex1-olefin copolymer may have a weight average molecular weight (Mw) in the range of 50,000 to 200,000.
In another embodiment of the present invention, the acid-modified butene-1/xcex1-olefin co-polymer may have a melting temperature in the range of 70xc2x0 C. to 100xc2x0 C.
In still another embodiment of the present invention, the organic solvent may comprise an alicyclic hydrocarbon having 5 to 8 carbon atoms in a proportion of 10 to 90% by weight.
In yet another embodiment of the present invention, the organic solvent may comprise an aromatic hydrocarbon in a proportion of 10 to 90% by weight.
In further another embodiment of the present invention, the resin solution composition may further comprise, as a curing agent, a compound having two or more epoxy groups per molecule.
A butene-1/xcex1-olefin copolymer used in the present invention comprises, as polymerizable components, 65 to 85 mol % butene-1 component, and 15 to 35 mol % C2-C8 xcex1-olefin component other than butene-1 component.
As the C2-C8 xcex1-olefin component other than butene-1 component, there may be mentioned ethylene, propylene, hexene-1, heptene-1, octene-1, 4-methylpentene-1 and the like, which may be used alone or in combination. Specific examples of the butene -1/xcex1-olefin copolymer include, for example, butene-1/ethylene copolymer, butene-1/propylene copolymer, butene-1/ethylene/propylene terpolymer and butene-1/ethylene/octene-1 terpolymer. Of the above-mentioned xcex1-olefin components, ethylene, propylene and octene-1 are suitable because of the versatility of copolymers.
The content of butene-1 is in the range of 65 to 85 mol %, preferably 70 to 80 mol %. The content of the xcex1-olefin component ranges from 15 to 35 mol %, preferably from 20 to 30 mol %. Where the butene-1 content is less than 65 mol % (where the content of the xcex1-olefin component exceeds 35 mol %), the final acid-modified butene-1/xcex1-olefin copolymer has a low mechanical strength and a weak cohesive force. As a result, the coating shows an inferior adhesion property to polyolefins. On the other hand, where the butene-1 content is over 85 mol % (where the content of the xcex1-olefin component is less than 15 mol %), the final acid-modified butene-1/xcex1-olefin copolymer has a melting temperature of 100xc2x0 C. or higher. In this case, the coating shows a poor adhesion property after low-temperature baking or heat sealing is practiced at 100xc2x0 C. or lower in paint or adhesive applications. Besides, depending on the molecular weight, the final acid-modified butene-1/xcex1-olefin copolymer shows an insufficient solubility in an organic solvent and, hence, a poor storage stability. It should be noted that the melting temperature of a polybutene-1 homopolymer is in the range of 122 to 130xc2x0 C., whereas that of a polybutene-1 homopolymer modified with an unsaturated carboxylic acid or its anhydride ranges from 110 to 125xc2x0 C.
This butene-1/xcex1-olefin copolymer can be modified with an unsaturated carboxylic acid or an anhydride thereof to give an acid-modified butene-1/xcex1-olefin copolymer.
The unsaturated carboxylic acid or its anhydride used herein includes unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and citraconic acid; unsaturated carboxylic anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride and endomethylenetetrahydrophthalic anhydride. They may be used alone or in combination. Considering the adhesion property of the coating and the price, maleic anhydride is particularly suitable.
This acid-modified butene-1/xcex1-olefin copolymer contains the unsaturated carboxylic acid or its anhydride in a proportion of 0.5 to 5% by weight, preferably 1 to 4% by weight. If the proportion of the unsaturated carboxylic acid or its anhydride is below 0.5% by weight, the acid-modified butene-1/xcex1-olefin copolymer not only shows a poor solubility in an organic solvent but also limits the adhesion property of the coating. Conversely, where the proportion of the unsaturated carboxylic acid or its anhydride exceeds 5% by weight, the coating properties are unsatisfactory. In particular, increase of polarity degrades the water resistance.
The butene-1/xcex1-olefin copolymer is modified with the unsaturated carboxylic acid or its anhydride in a known manner. In a typical reaction, the butene-1/xcex1-olefin copolymer is allowed to react with the unsaturated carboxylic acid or its anhydride in the presence or absence of a solvent (e.g. toluene, xylene) with or without addition of a radical initiator (e.g. benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, cumene hydroxyperoxide, 2,2xe2x80x2-azobis(isobutyronitrile)). This reaction is carried out under heating at as high as 70 to 250xc2x0 C.
Preferably, the resulting acid-modified butene-1/xcex1-olefin copolymer has a weight average molecular weight (Mw) ranging from 50,000 to 200,000, particularly from 60,000 to 150,000. If the Mw is below 50,000, the acid-modified butene-1/xcex1-olefin copolymer may lack a cohesive force, which causes the coating to show a poor adhesion property. On the other hand, the acid-modified butene-1/xcex1-olefin copolymer with a Mw over 200,000 decreases the fluidity of a resin solution composition which contains the copolymer in a dissolved state. Insufficient fluidity makes formation of a smooth adhesion layer difficult, when this resin solution composition is coated and dried under heating. In the present invention, the Mw is measured with the use of gel permeation chromatography (GPC), based on polystyrenes.
The melting temperature of the acid-modified butene-1/xcex1-olefin copolymer is preferably in the range of 70 to 100xc2x0 C. The copolymer with a melting temperature below 70xc2x0 C. may decrease the heat resistance of the coating. On the contrary, where the copolymer has a melting temperature over 100xc2x0 C., the coating may show an inferior adhesion property after low-temperature baking or heat sealing is practiced at 100xc2x0 C. or lower in paint or adhesive applications. To put it another way, in paint or adhesive applications (particularly, adhesive applications), it is desirable to bake or heat-seal the coating at a temperature higher than the melting temperature of the acid-modified butene-1/xcex1-olefin copolymer. The melting temperature mentioned in the present invention is based on the value measured by a differential scanning calorimeter.
In the acid-modified butene-1/xcex1-olefin copolymer, the crystallinity is not particularly limited. For example, a preferable crystallinity is in the range of 30 to 60%, as obtained by splitting the waveform measured by the wide-angle X-ray diffractometry, in order that the acid-modified butene-1/xcex1-olefin copolymer can retain a sufficient cohesive force and a proper solubility in an organic solvent.
The thus obtained acid-modified butene-1/xcex1-olefin copolymer is dissolved in an organic solvent to give a resin solution composition. The organic solvent used herein includes alicyclic hydrocarbons, aromatic hydrocarbons and the like. Desirable alicyclic hydrocarbons are those with 5 to 8 carbon atoms such as cyclopentane, cyclohexane, methyl-cyclohexane, ethylcyclohexane and cycloheptane, each of which has a boiling point acceptable for the organic solvent. Examples of the aromatic hydrocarbons are toluene, xylene, and other aromatic petroleum-mixed solvents which are sold on the market.
The alicyclic hydrocarbons and the aromatic hydrocarbons mentioned above are good solvents to the acid-modified butene-1/xcex1-olefin copolymer, which is hydrophobic. If any of these solvents is used alone, however, the solution of the acid-modified butene-1/xcex1-olefin copolymer may gelate within 10 days of storage at 25xc2x0 C. or lower. Hence, in the present invention, it is preferable to use a mixed solvent composed of an alicyclic hydrocarbon and an additional organic solvent, or a mixed solvent composed of an aromatic hydrocarbon and an additional organic solvent.
The additional organic solvent for constituting the mixed solvent includes not only the alicyclic hydrocarbons and the aromatic hydrocarbons mentioned above, but also aliphatic hydrocarbons such as hexane, heptane and mineral oils; esters such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol and 2-propanol; cellosolves such as ethyl cellosolve and butyl cellosolve. These organic solvents may be used alone or in combination. Above all, organic solvents having a carbonyl group (i.e. esters and ketones) are preferable, because they can surely prevent the solution of the acid-modified butene-1/xcex1-olefin copolymer from gelating during along period of storage at 25xc2x0 C. or lower. These solvents are also recommended in terms of miscibility with the alicyclic hydrocarbons or the aromatic hydrocarbons and solubility of the acid-modified butene-1/xcex1-olefin copolymer. Such esters and ketones, which have high affinity for a polar group of the acid-modified butene-1/xcex1-olefin copolymer (i.e. carboxyl group or acid anhydride group), are considered to enhance the dispersability of the copolymer in the organic solvent.
The mixing ratio of the alicyclic hydrocarbon or the aromatic hydrocarbon relative to the additional organic solvent may vary, depending on the amount of unsaturated carboxylic acid or its anhydride contained in the acid-modified butene-1/xcex1-olefin copolymer. By way of example, where the mixed solvent comprises an alicyclic hydrocarbon and an additional organic solvent, the content of the alicyclic hydrocarbon is preferably in the range of 10 to 90% by weight, particularly 20 to 80% by weight. Likewise, in the mixed solvent comprising an aromatic hydrocarbon and an additional organic solvent, the content of the aromatic hydrocarbon is preferably in the range of 10 to 90% by weight, particularly 20 to 80% by weight. If the alicyclic hydrocarbon content is lower than 10% by weight, the solution of the acid-modified butene-1/xcex1-olefin copolymer may gelate in the opaque state within 10 days of storage at 25xc2x0 C. or lower. On the other hand, if the alicyclic hydrocarbon content is over 90% by weight, the solution of the acid-modified butene-1/xcex1-olefin copolymer may turn into a highly viscous transparent solution, and gelate in the transparent state within 10 days of storage at 25xc2x0 C. or lower. Similar tendencies are recognized when the aromatic hydrocarbon is employed in place of the alicyclic hydrocarbon.
In the resin solution composition, the solid content of the acid-modified butene-1/xcex1-olefin copolymer is in the range of 10 to 30% by weight, preferably 15 to 25% by weight. A solid content lower than 10% by weight, or an organic solvent content of over 90% by weight, is unsuitable for paint or adhesive applications, in view of the cost and the recent issues on Volatile Organic Compound (VOC) control. Besides, during the preparation of paints, pigments may not disperse well in a resin solution composition with such a low solid content. On the contrary, with a solid content over 30% by weight, the solution of the acid-modified butene-1/xcex1-olefin copolymer may gelate in the opaque state within 10 days of storage at 25xc2x0 C. or lower.
Additionally, the resin solution composition of the present invention may comprise, as a curing agent, a compound having two or more epoxy groups per molecule. This epoxy group-containing compound helps to further enhance the properties of the coating. Nonetheless, due to safety and hygiene problems, some kinds of epoxy group-containing compounds cannot be employed as a material for paints or adhesives. With this point borne in mind, the epoxy group-containing compounds are properly selected in accordance with intended applications.
As the epoxy group-containing compounds usable in this invention, there may be mentioned bisphenol A-type epoxy resins obtained by a condensation reaction of bisphenol A with epichlorohydrin; glycidyl ethers of polyhydric alcohols, such as ethylene glycol glycidyl ether, propylene glycol glycidyl ether and trimethylolpropane triglycidyl ether; polymers which contain glycidyl (meth)acrylate as a polymerizable component, and the like.
The added amount of epoxy group-containing compound is not strictly limited, and preferably such that the amount of epoxy is fivefold equivalent or less relative to the amount of unsaturated carboxylic acid or anhydride thereof contained in the acid-modified butene-1/xcex1-olefin copolymer. If the epoxy group-containing compound exceeds this range, the coating may show undesirable properties (in particular, the adhesion property to polyolefins). At the same time, considering the compatibility between the acid-modified butene-1/xcex1-olefin copolymer and the epoxy group-containing compound, the storage stability may be adversely affected.
Unless departing from the object of the present invention, the resin solution composition of the present invention may contain, where necessary, resins used for paints or adhesives such as alkyd resins, urethane resins and acrylic resins; pigments, stabilizers and other components.